Method and apparatus for cutting panels

ABSTRACT

This is concerned with a panel-cutting machine and is specifically concerned with apparatus for securely holding a stack of sheet material with respect to a cutting station while a cutter traverses along its cutting path through the material. The material is indexed for gauging along an axis and a pair of holddowns are used in which each is mounted at the cutting station traversely of the axis on either side of the cutting path for movement to and from the stack on the stack side opposite the cutter.

United States Patent Campbell [451 Oct; 30, 1973 54] METHOD AND APPARATUS FOR CUTTING 2,908,300 1011950 train};...'.'.ll.;..l.l lulu/0 PANELS 2,083,419 6/1937 Andrews.... 269/34 X 3,625,102 12/1971 Shiino 83/460 [75] Inventor: James W. Campbell, Fort Worth,

Tex. FOREIGN PATENTS OR APPLICATIONS [73] Assignegz Halton y state Bank, Fort 697,254 11/1964 Canada 83/461 worth P E G n Y c J w rimary xaminerranvi e uster, r. [22] Filed Sept An0rney--Parker, Plyer and McEachron [21] Appl. No.: 71,107

Related US. Application Data [62] Division of Ser. No. 805,943, Feb. 17, 1969, Pat. No.

[52] U.S. Cl. 269/34 [51] Int. Cl. 823g 3/08 [58] Field of Search 83/389, 460, 461; 143/132 F; 269/34 [56] References Cited UNITED STATES PATENTS 1,200,802 10/1916 Berry 83/460 X 2,025,330 12/1935 Brownlow... 143/86 2,077,118 4/1937 Lewis 143/132 F Z7 Z1 1 25 E I l [57] ABSTRACT This is concerned with a panel-cutting machine and is specifically concerned with apparatus for securely holding a stack of sheet material with respect to a cutting station while a cutter traverses along its cutting path through the material. The material is indexed for gauging along an axis and a pair of hold-downs are used in which each is mounted at the cutting station traversely of the axis on either side of the cutting path for movement to and from the stack on the stack side opposite the cutter.

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Patented Oct. 30, 1973 15 Sheets-Sheet Mm 3 IJ Lh- L L u Patented Oct. 30, 1973 13 Sheets-Sheet 2,)

Patented Oct. 30, 1973 3,768,796

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13 Sheets-Sheet 12 ZZZ METHOD AND APPARATUS FOR CUTTING PANELS This application is a division of copending application Ser. No. 805,943, filed Feb. 17, 1969, now U.S. Pat. No. 3,662,798, issued May 16, 1972.

SUMMARY OF THE INVENTION This invention relates to the production of eut-to-size panels from sheets of material and more particularly relates to the method and apparatus for cutting accurately dimensioned panels in an unlimited combination of sizes and shapes in fully automatic, efficient steps.

The invention provides a superior method of producing accurately dimensioned cut-to-size parts from larger sheets of particleboard, hardboard, plywood,

and related panel materials. Panels of this type would find use in many applications, as for example in furniture making, home building, T.V. and radio cabinet production, and the like.

Present practice is to roughly cut sheets of the material into over-sized panels which may be shipped to the manufacturer for further trimming to the finished dimensions. This means that the manufacturer must provide costly cutting equipment and manpower for the finishing operations. The present invention eliminates the need for finishing by the manufacturer since the supplier can produce panels of the exact dimension specified, and guarantee the results.

Conventional cutting equipment is not fully automatic in that single panels are manually set-up and clamped, after which a gang of saws are moved across the sheet. Following this, the panels are again set-up by the operators for the cut-off operation. The present invention is much more efficient in that sheets are stacked and simultaneously cut to increase output, and virtually no time is required for set-up. Also, only one operator is required to run the machine since the panels are moved from station to station and gauged for cutting in a fully automatic operation.

The extreme accuracy obtainable with the invention not only reduces the need for finishing operations but also reduces the trim and scrap losses. By carefully selecting the patterns cut from the sheet a maximum number of panels may be made from a given square of stock without waste. Once this is set up the machine can automatically reproduce the various cutting operations in the same sequence an unlimited number of times. Alternatively, the operator can readily adjust the control circuitry and selectively after the pattern cut from the sheets so that the dimensions and shapes of the end product may be varied in any manner. There is no machine down-time in order to change one cut pattern to another.

Productivity is further increased as a result of saw sensing controls which automatically return the saw after completing a cut, no matter what the sheet width may be, so that sawing time is reduced.

The invention will produce panels with improved finished part quality, particularly in terms of smoothness ofcut. A factor in this is the automatic control of linear saw speed as a function of load as well as stack cutting.

The machine comprises a number of integrated units performing a series of stacking, gauging, ripping, and cross-cutting operations. The units are arranged along a pair of perpendicular axis. The infeed, stacking and rip cutting operations are performed along the first axis and the cross-cutting operation produces the finished panels along the second axis.

The stock of sheet material is first placed on a charging roll unit which delivers it to a stack infeed station. At the stack infeed the sheets are counted and moved onto a gauge unit for the rip operation, either singly or in a stack. The stack infeed can either pick offa predetermined number of single sheets to form a stack, or else push a stack of predetermined height across a gate onto the gauge table. The pusher moves this stack by means of an hydraulic motor which has a stroke comprised of two variable velocities: a rapid initial velocity which is maintained during most of the travel for machine efficiency, and a slow final velocity to bring the stack to a stop at an accurate location without sliding.

At the gauge table clamp arms grip the stack to securely hold the sheets together, and the stack is then indexed towards a rip saw unit through predetermined distances according to the pattern to be cut. Each time the stack is moved to a stop the driving motor is decelerated at an optimum rate for accurate positioning and to eliminate drive train overshoot.

The clamps establish a reference line with respect to either saw unit so that before each cut the clamps and reference line are advanced a predetermined distance. This positions the stack so that the saw unit will then cut off a stack of panels having common widths equal to the predetermined distance.

The clamps are of the caliper type adapted to float on their supporting carriage unit so that clamp carriage weight is not transferred to the panel stack.

At either the rip or cross-cut saw units automatic hold-downs are provided to press the stack against the gauge table as the saw, moving from underneath, makes its cut through the material. The hold-downs are operated by pairs of hydraulic cylinders connected in a hydraulic circuit such that opposite sides of each hold-down are powered up in parallel and down in series.

At the junction of the two machine axes a rip run-out unit is provided to receive material cut by the rip saw. This unit is adapted to either feed trim and scrap from the machine in one direction, or to reverse itself and feed the panels to the cross-cut saw along the second axis. As the panels move onto the second gauge infeed they are automatically aligned by a movable fence.

The cross-cut operation is performed with a gauge unit substantially identical to the first axis equipment but with a plurality of belts on the gauge table to move the panels into position for clamping. The panels are clamped together and advanced toward the saw for accurately dimensioned cross-cutting.

At the cross-cut location hydraulically operated hold-downs operate in a manner identical to the first axis hold-down unit.

As the finished panels move away from the cross-cut saw the scrap will automatically fall through an adjustable slot in the table for removal to either side of the machine by an endless belt.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a panel cutting machine incorporating features of the invention;

FIG. 2 is a plan view in schematic form illustrating the flow of material through the units of the machine;

FIG. 3 is an elevation view of a section of the machine illustrating a portion of the charging roll unit, the stack infeed, and a portion of the gauge unit;

FIG. 4 is a plan view of the stack infeed of FIG. 3;

FIG. 5 is a sectional view taken along the line 55 of FIG. 4 on an enlarged scale;

FIG. 6 is a sectional view to an enlarged scale taken along line 6-6 of FIG. 5 illustrating the pusher assembly for the stack infeed;

FIG. 6a is a partial view of the pusher assembly of FIG. 6 illustrating single panel infeed;

FIG. 7 is a view similar to FIG. 6 illustrating a modified pusher assembly adapted for single panel infeed;

FIG. 8 is a sectional view to an enlarged scale taken along line 8-8 of FIG. 3;

FIG. 9 is an elevation view illustrating the relationship of the stack infeed, gauge unit, rip saw unit and rip run-off showing the pusher assembly moving a stack;

FIG. 10 is an enlarged view of a portion of FIG. 9 illustrating indexing of a stack to a sawing operation;

FIG. 11 is a side elevation view of the rip saw illustrating movement of the saw and carriage along the work piece;

FIG. 12 is a side elevation view, partially broken away, of a typical hold-down unit at a saw location;

FIG. 13 is a sectional view taken along the line l313 of FIG. 12;

FIG. 14 is a top plan view of the rip saw, rip run-out, and a portion of the cut-off infeed unit;

FIG. 15 is a top plan view similar to FIG. 14 and to a reduced scale diagrammatically illustrating movement of the work material through the machine;

FIG. 16 is a top plan view similar to FIG. 15 of the cut-off infeed illustrating movement of the work material;

FIG. 17 is an enlarged side elevation view illustrating alignment of the work material on the cut-off infeed by snubbing action of the clamps;

FIG. 18 is a side elevation view as viewed along line 1.8-18 of FIG. 14 illustrating the drive arrangement for the rip run-out and cut-off infeed.

FIG. 19 is a side elevation in partial section of the output end for the cut-off infeed drive;

FIG. 20 is a detail side elevation view on an enlarged scale of the output end for the cut-off infeed drive;

FIG. 21 is an elevation view in section taken along line 21-21 of FIG. 19 on an enlarged scale;

FIG. 22 is an end elevation view in section on an enlarged scale taken along line 22-22 of FIG. 15 showing the four-bar work alignment mechanism;

FIG. 23 is a side elevation view of the gauge unit, cross-cut saw station, and scrap discharge for the cutoff operation;

FIG. 24 is an enlarged side elevation view of a portion of the gauge unit of FIG. 3;

FIG. 25 is a top plan section view on an enlarged scale taken along line 2525 of FIG. 24;

FIG. 26 is an enlarged elevation view, partially sectioned, of the scrap discharge unit of FIG. 23;

FIG. 27 is a diagram illustrating the control circuit for a typical hold-down unit of FIGS. 12 and 13;

FIG. 28 is a diagram illustrating the control and operation of the servo motors for the gauge carriage; and

FIG. 29 is a graph illustrating operation of the servo motors of FIG. 28.

DETAILED DESCRIPTION Referring to the drawings and particularly FIG. 1, the preferred embodiment of the panel cutting machine is illustrated generally at 10. Machine 10 comprises a charging roll unit 12, a stack infeed section 14, a first gauge unit 16, a rip saw unit 18, a rip hold-down 19, a rip run-out 20, a cut-offinfeed 22, a second gauge unit 24, a cross-cut saw unit 26, a cross-cut hold-down 27, and a cut-off scrap and finished panel discharge unit 28.

A panel cutting operation is initiated by depositing stacked sheets of work material on charging roll unit 12 by means of a forklift truck, conveyor, or other suitable means. The work material may be particleboard, hardboard, plywood, and other related panel materials.

Machine 10 is adaptable for cutting work material of a variety of sizes and thicknesses into finished panels of any desired dimensions with a high degree of accuracy. As shown in FIG. 2 the work material deposited at charging unit 12 is serially conveyed along axis Y for counting, stacking, clamping and gauging for transverse rip sawing into panel sections. Excess trim from this sawing is then discharged away from the machine and the panel sections are conveyed at right angles along axis X for alignment, clamping, gauging and cutoff sawing with automatic scrap discharge as the finished panels move from the machine.

CHARGING ROLL UNIT 12 Referring to FIG. 3 a portion of the charging roll unit 12 is illustrated in greater detail. This unit comprises a frame 30 supporting a plurality of spaced, powerdriven rollers 32. A suitable motor 34 and drive train 36, which may be of the link-chain or belt type, simultaneously drive the rollers under control of a suitable central control system, not shown. The stacked sheets of work material placed on unit 12 are then driven across idler roller 38 into stack infeed 14. The charge of work material moved into the infeed may be of any given number of sheets but typically would be sufficient for charging the machine with a number of stacks, depending upon sheet thickness, for continuous sawing operation.

STACK INFEED 14 Stack infeed 14 provides a combination single or multiple panel infeed function. Single panels may be automatically counted off from the charging stack and moved onto gauge unit 16, or else a stack of predetermined height can be moved as a unit. Either method will feed a predetermined number of stacked sheets for subsequent cutting operations, and thus may be automatically varied by the control system according to the number of finished panels desired.

Referring to FIGS. 3 and 4 stack infeed 14 includes an elevator assembly 40 working in coordination with pusher unit 42. The elevator assemblycomprises a platform 44 mounted for vertical movement along four upstanding columns 46, 48, 50, 52 mounted on a suitable foundation. A plurality of spaced-apart rollers 54 are mounted within the elevator assembly. Rollers 54 are simultaneously driven by a suitable motor 56 and drive train 58 to move the work material forward over the platform in timed relationship with charging roll unit 12. The rollers, motor, and drive train are preferably mounted for vertical movement with platform 44, al-

though it could be otherwise with these components suitably anchored to the machine frame or foundation between columns 4652 and with lateral slots in the platform surface exposing the roller tops.

Elevator 40 is powered up and down by means of threaded shafts 60 rotatably mounted adjacent each column. Each shaft threadably engages respective nuts 62 secured to the corners of platform 44. The threaded shafts and elevator may be powered by any suitable means, preferably a pair of electric motors 64 and 66 geared to laterally extending drive shafts 68,70. The drive shafts are connected directly through uitable gearing with each shaft in columns 46, 52 and through a pair of chain drives 72, 74 and bevel gearing with each shaft in column 48, 50.

Motor 66 is connected with drive train 76 to move elevator 40 down and motor 64, which preferably has a higher power capacity, is connected through couplings 78 to drive the elevator up, both motors being controlled in timed relationship with pusher assembly 42 to move a predetermined number of sheets resting on the elevator into the proper elevation to be moved forwardly onto gauge unit 16. Although a pair of electric motors are shown, it is understood that other types of motive power means could be used to elevate the work material in the manner described.

Pusher unit 42 is illustrated in FIGS. 3-7 and comprises a plurality of laterally spaced pusher assemblies 80 mounted on a pair of side-by-side carriages 82, 84 which in turn are mounted for traversing movement along the length of overhanging frame 86. Although a pair of carriages 82, 84 are illustrated, the number employed in any particular design would depend on the number of pusher units and maximum sheet width capacity.

Overhanging frame 86 comprises four U-section beams 88, 90, 92, 94 secured at opposite ends by suitable braces 96, 98 and at intermediate locations to columns 46-52, with crossbracing provided by a pair of beams 100, 102. The overhanging ends of frame 86 are suspended from beams 100, 102 by means of a plurality of cables 104. A platform S mounted above beams 100, 102 is provided to mount the motors and drive arrangement for elevator 40. A trolley rail or track 107 is mounted in each of the beams 88-94 lengthwise of the frame.

Each carriage 82, 84 comprises a frame or platform 106 mounted to roll along frame 86 by means of a plurality of grooved wheels 108 rotatably mounted to platform 106 and guided along rails 107.

Traversing movement of pusher unit 42 is controlled by operation of motor 110 and drive train 112 mounted at the forward end of frame 86 and functioning in timed relationship to elevator operation in accordance with the predetermined program. As illustrated in FIG. 4 motor 110, which preferably is a conventional rotary hydraulic motor powers countershaft 114 through drive train 112 and sprocket 116. Rotation of countershaft 114 traverses pusher unit 42 forward and backward by a suitable drive train, preferably a plurality of link chains 118 trained between drive sprockets 120 and idler sprockets 121, with the free ends of the chains anchored by suitable means to the pusher units, as illustrated in FIG. 6.

Each pusher assembly 80 comprises a pusher arm 122 pivoted at 124 to a bracket 126 depending from and bolted to pusher platform 106. A plurality of such pusher assemblies are provided at laterally-spaced positions 128, 130 along each of the carriages 82, 84, although only one such assembly 80 is illustrated in FIG. 5 for clarity.

Pusher arms 122 are pivoted downwardly by means of springs 132 each connected between stop bar 134 on the carriage and the rearward portion of the arm. Each arm may be secured upwardly in an inoperative position, illustrated by dashed lines, with a pin or bolt inserted through hole 135 in bracket 126 and a registering hole, not shown, in the arm. This would be desirable where one or more of the arms are not needed, as when the sheet width is less than the maximum capacity of the machine.

When pusher unit 42 is at its maximum rearward travel indicated in FIG. 3 pusher arm 122 moves downwardly to an extent determined by means of adjustable cap screw 136 between stop bar 134 and the arm. This adjustment prevents the arm from hitting gate 144, illustrated in FIG. 3, during infeed operation. A stop bar 137 may be mounted on arm 122 with an adjustable stop or cap screw 139 engaging the top of stack 140. This determines the extent that forward face 18 of the arm projects below the stack. The elevator in turn elevates the stack so that a predetermined height thereof extends above upper edge 142 of gate 144. Gate 144 forms the forward wall of gauge unit 16 so that the stack height extending above gate edge 142 is moved directly onto the top of gauge unit 16 by the pusher unit as it moves forward. This strips off the desired number of sheets. Gate 144 is vertically adjustable by suitable means, such as a slot and bolt arrangement, to accurately position it relative to the elevator.

After pusher unit 42 reaches the extent of its forward travel on frame 86 to move the material stack to a stop on the gauge table the control unit reverses motor 110 to return the pusher unit to its rearward position for the next feeding cycle. At the same time elevator 40 indexes upwardly a predetermined height to position the next work material for charging.

For relatively large panels, on the order of from three-fourths to 2 inches in thickness, measurement of stack height above gate edge 142 is accurate enough to determine the number of sheets which the pusher arm will strip off as a unit for feeding. On thinner panels, on the order of from one-eighth to three-fourths inch in thickness, it has been found expedient to feed a single panel at a time from the elevator. The control system counts the number of panels thus moved until the desired number is deposited on the gauge unit.

Single panel feeding may be provided by the arrangement of FIG. 6 and 6a in which a pusher roller or wheel 145 is mounted on each arm 122. Roller 145 preferably comprises a rubber tired friction wheel rotatably mounted by means of a conventional cam (one-way) clutch 147 which locks up the wheel as it moves forwardly to produce a high static friction between the tires and the top sheet. The control system operates hydraulic motor 110 by an abrupt opening of its valve control to develop the highest force for the tire static friction at the instant the sheet is to start sliding from the stack. This abrupt start overcomes the static friction between the top and second sheets since the combined friction of the rubber tires is many times greater than the friction of sheet on sheet. Clutch 147 operates to freely rotate the wheel as it moves rearwardly over the stack and returns for stripping off the next sheet. As

each sheet is stripped off, spring 132 pivots arm 122 to provide pressure on roller 145 and increase tire friction against the sheet.

A ramp 151 is secured to the underside of each arm 122. The ramp preferably comprises a metal strip welded to the arm with a ramp surface 153 inclined downwardly and forwardly to a position just clearing the bottom of wheel 145. As each sheet is stripped off roller or wheel 145 will drop from the leading edge of the stack while arm 122 pivots downwardly. During rearward return of the pusher unit ramp surface 153 contacts the front edge of the next sheet on the stack and guides the arm upwardly until the wheel makes contact. The ramp insures that the wheel contacts the top sheet at a relatively small angle with respect to the vertical. Otherwise the wheel could strike the sheet with such force that it would be displaced to the rear.

To insure effective frictional contact between wheels 145 and the stack means are provided to continually remove any dust material which may collect. Preferably this comprises a pair of brushes 155, 157, such as nylon bristle brushes, mounted on arm 122. Brush 155 is positioned to wipe dust from the wheel while brush 157 clears the wheel path as the wheels roll back over the stack.

FIG. 7 illustrates a modification which provides positive stripping action for single panel feeding. A pusher tang 146 is pivotally mounted at 148 to arm 122. An adjusting cap screw 149 is mounted at the forward end of the tang for engagement with a laterally extending dowel 150 secured to arm 122. A supporting roll or wheel 152 is rotatably mounted on the arm at 154 to carry it over the upper surface of material stack 1S6. Adjustment of cap screw 149 will selectively vary the extent of tang 146 overhang below wheel 152 to compensate for variations in sheet thickness.

For single panel feeding stop bar 137 may be removed from arm 122, as desiredl.

As the pusher unit of FIG. 7 advances the tangs 146 of each pusher assembly will engage the rearward edge of the top sheet and move it forward for deposit onto the top of gauge unit 16. As the pusher unit returns the tangs 146 pivot upwardly upon engaging the stack, and wheel 152 rolls over the surface of the top sheet. When the pusher unit returns to its initial rearward position the tangs will clear the rear edge of the stack and drop down for engaging the next sheet. This cycle is repeated a predetermined number of times until the desired number of sheets are deposited on the gauge unit. As required, elevator 40 may be indexed upwardly a height sufficient to position the stack for the feeding cycles.

After the desired number of sheets are on the gauge unit just forward of gate 144, the control system lowers elevator 40 so that the charge stack is free of the pusher unit, as indicated at 158 in FIG. 9. Pusher arm 122 then drops downwardly by gravity and the action of spring 132 to the position of FIG. 6, and motor 110 is energized. This traverses pusher unit 42 forward so that pusher arm 122 engages stack 160 and moves it forwad to clear the gauge clamps, as shown in FIG. 9. Following this thepusher unit is returned to its rearward position of FIG. 3 and the elevator raises the stack for the next infeed charge. The controls now operate the machine through the gauging cycle.

Hydraulic pusher motor 110 accurately positions the stack on the gauge table for clamping. Known parame ters of the frictional coefficients of the stack and gauge table, the stack inertial forces, and motor driving forces are predetermined and integrated into the central control system. The central control signals motor 110 to operate at a rapid initial velocity maintained during most of the travel for machine efficiency, and a slow final velocity to bring the stack to a stop without sliding beyond the preselected location.

GAUGE UNIT 16 Referring to FIGS. 3, 8 and 9 gauge unit 16 comprises a gauge table 162 for supporting panel stack 160, gauge clamps 164 for clamping the stack, and clamp carriage 166 for moving the clamped stack along the gauge table in relation to saw unit 13.

Gauge table 162 comprises a plurality of longitudinally extending plates 168 having downwardly extending side flanges 170, 172 spaced apart to define a slot or channel through which respective gauge clamps 164 traverse to and from the saw unit. Plates 168 are mounted at their rearward end by suitable means such as frame 174, and at their forward end on saw unit 18.

Gauge carriage 166 comprises a carriage frame 176, FIGS. 3 and 8, supported at either side by pairs of wheels 178, mounted in suitable anti-friction bearings. The wheels are guided on a track 182 mounted on the top of a beam 184 mounted lengthwise between frame 174 and saw unit 18.

Carriage 166 is driven along the rails by means of a conventional hydraulic servo-type motor 186 to provide accurate positioning of the carriage, and thus the clamps and stack, with respect to the saw location. This eliminates any gauging error which might be produced by backlash in the transmission. Motor 186 powers the carriage through a suitable drive connection, which may include connector 188, worm gear reducer 190, connecters 192, 194, shafts 196, 198, and pinion gears 200,20 which drivingly engage racks 204,206 mounted on the inside of beams 184. The control system directs a given distance command or signal, depending on the desired gauging displacement of carriage 166, into motor 186 which turns a predetermined number of revolutions to drive the carriage through the rack and pinion arrangement.

Deceleration of the load is such that the stack is pushed to a stop by servo motor 186 so that the stack can be accurately positioned relative to the saw. Otherwise the stack could coast beyond the desired saw location. At the same time, any slack in the carriage drive train is continually taken up so that such slack does not affect gauging.

The diagram of FIG. 28 illustrates the construction and operating control system for servo motor 186, and it is understood that servo motor 460 for gauge unit 24 is similar in construction and operation. These motors can be either digital or analog hydraulic servo motors. One example would be an electrohydraulic pulse motor in which each stop of its electric motor is followed by a stop of the hydraulic motor output shaft connected with the transmission to drive load 159, which would include the stack.

The high speed electric stopping motor 161 follows the input command pulses or signals originating from the control system at 163 to drive reduction gear train 165. This gear train reduces the rotation of motor 161 to a fixed anglo per signal, and in turn operates fourway pilot valve 167, consisting of a rotary-linear spool and sleeve. Valve 167 controls fluid flow from hydraulic power supply 169 into axial type fixed-displacement hydraulic motor 171 proportional to the relative deviation of spool and sleeve. The rotating speed of motor 171 is proportional to the flow rate from the valve, with mechanical feedback 173 provided through a nut fixed to the motor shaft and a screw fixed to the valve spool reducing relative deviation between the spool and sleeve.

The graph of FIG. 29 illustrates the operation of the servo motors, with stack velocity indicated as a function of unit distance along the gauge table. Assuming that the stack load is moving along the gauge table by the gauge carriage, there is a normal drag as a result of sliding friction on the table. If the driving force were completely removed the load would come to a stop following the curve indicated at 175, as an example. With applicants invention the control system of FIG. 28 is adjustable as to initial velocity 177 and final velocity 179, with a precalculated exponential fixed rate change 181 decelerating the load while maintaining a driving force, instead of removing it as in a freely sliding stop. When the load reaches velocity 179, which is at a very low value, the driving force is then removed and the small amount of kinetic energy remaining within the moving masses is absorbed in these masses as well as the machine structure, thereby allowing an instantaneous stop at an accurately located position 183.

The control system is preset using the known frictional coefficients of the stack and gauge table, the inertial forces of the stack, gauge clamp and carriage, and the driving force of motor 186 so that the energy input is always greater than the kinetic energy during a freely sliding stop. This insures that the stack is decelerated to and does not slide beyond, the desired location.

Each of the identical gauge clamps 164 is secured to carriage 166 by means of a lateral support 208 integral with and forming the forward support for the carriage. Each gauge clamp is mounted on the carriage in a floating arrangement best illustrated in FIG. 24 showing the arrangement for gauge clamp 210 of gauge unit 24 on the X axis.

Each of the gauge units 16 and 24 are of substantially identical construction with indentical gauge carriages, tables and clamps. FIG. 24 illustrates a modification for the X axis gauge clamp in which a double extension actuator is provided for alignment purposes, as will subsequentiy be explained. Except where parts may differ, identical reference numerals refer to corresponding parts for the two gauge units in all views.

Each gauge clamp 164, 210 comprises a caliper clamp type arrangement having a pair of laterally spaced-apart lower jaws 212 and a single upper jaw 214 vertically movable from its lowered, nestled position between the lower jaws (FIG. 3) and to its upper, extended position (FIGS. 8, and 24). Lower jaws 212 are supported at their forward end by cross brace 216, and a slot 218 is provided in the upper jaw to clear this support when lowered. Each of the lower jaws 212 has a rear support or extension 220. The upper jaw has a rearward support or extension 222 mounted for vertical sliding movement between supports 220 by means of a pair of mutually facing channel members 224, 226 secured together by suitable fasteners, such as bolts 228, 230.

Vertical movement of upper jaw 214 is effected through operation of double-acting actuators 232 (Y axis) and 233 (X axis), which preferably are air operated, although they could be hydraulic rams or the like. The actuators are connected at one end to upper jaw extension 222 at 234 and at their lower end to a bracket 244 secured to four downwardly extending supports 236, 238, 2469, 242 bolted to lower jaw supports 220.

For clamp 164 on the Y axis actuator 232 preferably comprises a single air cylinder 246 secured at one end to support 244 and with the upper end of its rod secured to jaw support 222. In the modification of FIG. 24 for clamp 210 on the X axis actuator 233 comprises a pair of air cylinders 248, 250. Cylinder 248 is connected at one end to support 244, as above, and with cylinder 250 connected to jaw support 222 with its rod secured to the rod of cylinder 248 at connection 252. The function of the double ram modification is explained hereinafter in connection with FIG. 17.

The entire gauge clamp is arranged to float with respect to the carriage through a sliding connection 254, shown in FIG. 25. This comprises a pair of brackets 256, 258 secured to carriage support 208 by suitable means such as bolts 260 and brackets 262. Pairs of vertically aligned elongated slots 264 are formed in each bracket 256, 258. The clamps are slidably mounted within the slots by means of bushings 266 and spacers 268 mounted on bolts 230. Tension springs 270 mounted at one end to clamp support 240 and at their other end to carriage support 208 urge the gauge clamps upwardly in the slots with respect to the carriage and thereby support a part of the weight of the clamps and actuators.

With the clamps arranged to float in this manner the weight of the carriage is not added to the weight of the stack, and at the same time this prevents the upper clamp from applying any clamping force between the gauge table and stack. Part of the clamp weight is carried by the stack, with the remainder carried by the springs. Where only a few, light sheets are being gauged this added clamp weight will insure sufficient frictional drag to stop the stack in accordance with the preset program of the control system.

Referring to FIGS. 3 and 9 the gauge clamp is illustrated with cylinder 246 retracted so that upper clamp 214 is nestled between lower clamps 212, both of which thus have their top edges substantially flush with gauge table 162. With gauge unit 16 in its maximum rearward position stack is slid on the table by the pusher unit forward over the clamps to a position clearing the clamp forward edges, as illustrated in FIG. 9. Following this the pusher unit is moved rearwardly for its next cycle and the control circuit then actuates cylinder 246 to extend jaw 124 upwardly its maximum travel, servo motor 186 is actuated to move gauge carriage 166 forwardly until the clamp jaws overlap the rearward edge of stack 160, the carriage is stopped, and ram 246 retracted so that the jaws clamp the stack, as illustrated in FIG. 10. Overlapping of the jaws on the stack edge may be from one-half to 2 inches, as an example, and is calculated so as to provide adequate clamping without undue trim loss. Once the amount of overlap is set up into the control system, it need not be changed throughout repetitive cycling.

The stack is cantilevered out from the jaws and carriage, as shown in FIG. 24, in order to provide clearance for the gauge unit over the saw unit. This is a matter of the location of components and could be varied depending on the particular design configuration arrived at.

The clamping force is precalculated to insure against relative sliding of the panels for the slickest material which will be handled. This clamping force is coordinated with the inertial forces and the coefficient of friction between the panels for such material so that when the stack is decelerated to a stop no relative sliding of the panels occurs. It is important to prevent panel sliding for accurate gauging of the panel width and to insure that the cuts are square.

Although it is old to clamp stacked material for cutting, with applicants novel invention the entire stack is clamped and moved accurately relative to the saw as the method of gauging the rip and cut-off dimensions. This is accomplished by establishing a bench mark or reference line on the stack through means of the clamps and then accurately moving this reference line relative to the saw for each cutting operation.

The gauging operation by means of establishing such reference line is illustrated in FIG. 10. With stacked sheets 160 resting on table 162 and tightly gripped between the clamp jaws a reference line 272 is established in a position fixed with respect to the stacked panels. Although reference line 272 is indicated as aligned with a forward edge of upper jaw 214, the line could be located at other positions relative to the clamps with corresponding adjustments made in the control circuitry for gauging, as long as this reference line remains fixed after the parameters of the control operation are determined.

With the known, fixed reference line 272 established relative to the stack, and with the exact position of this reference line relative to saw location 274 ltnown, the exact distance a between the two is also known and sensed by the control system. The leading edge of the stack at this time is indicated by the dotted line at 276, FIG. 10.

The control system is now ready to initiate cycling of gauging for the first rip cut, which usually would be to trim the leading edge. The control circuit signals servo motor 186 to turn a predetermined number of revolutions and move gauge carriage 166 forward until reference line 272 reaches distance b from saw position 27 4. At this time the upper jaw is at the position indicated at 2114 while the leading edge of the stack overlaps the saw at 276' for trimming. Next, the control circuit signals hold-downs 19 and saw unit 18 to operate through their cycles and make a first rip cut. After this gauge unit 16 cycles through one or more subsequent gauging operations to move the stack forwardly for further rip cuts which separate the stack into one or more sections having accurately dimensioned and squared rip edges.

At the completion of the last rip cut just forward of upper jaw 214 pressure on the gauge clamps is released to free tail material 278, and the gauge carriage is moved backwards to the position of FIG. 9.

The leading trim portion at 276' and each of the panel sections cut by the machine are moved forward onto rip run-out 20 as the gauge unit indexes the stack for each following cutting operation. Stack tail material 278, released by the clamps, is moved forward onto rip run-out 20 by the subsequent stack being pushed forward for its trimming operation.

During gauging the predetermined distance which the control circuit moves the reference line 272 includes the kerf or width of saw cut made by the previous sawing operation. Thus, if it is desired to cut a panel of given width, then the control circuit would index the reference line forward this width plus the saw kerf width 280, which information is precalculated and fed into the control circuit.

After a saw blade is sharpened the new kerf cut by the blade is narrower than before. To compensate for this, information on the number of times the blade has been sharpened is fed into the control circuit so that the kerf compensating distance added to desired panel width for each gauging operation can be varied accordingly. For example, if a new blade is to be sharpened twice in use then three different kerf widths would be set into the control system, one each for sawing with a given blade condition.

SAW UNITS l8 and 26 Referring to FIGS. 11 and 14 rip saw unit 18 is illustrated, and it is understood that cross-cut saw unit 26 is substantially identical in construction and operation.

Saw unit 18 comprises a frame 282 supporting a pair of laterally extending rails 284, which may be elongated rods mounted on a plurality of cushion blocks 286, the positioning of which is illustrated in FIG. 23 for cross-cut saw unit 26. A saw carriage 288 is mounted for sliding movement on the rails by means of four bearing blocks 289. An arbor housing 290 is pivotally mounted on the carriage at 292 and an extensible actuator 294, preferably an air operated cylinder, is mounted on the carriage to pivot the arbor housing between the raised position of FIG. 11 and its lower position.

A circular saw blade 296 is rotatably mounted on housing 290 by means of arbor 298. Housing 290 mounts a saw motor 300, preferably an electric motor, which powers the saw through drive train 302.

Saw carriage 288 traverses along the rails by means of the preferred reversible hydraulic motor 304, illustrated in FIGS. 11 and 14, mounted on frame 282. This motor is drivingly connected to the carriage by means of drive train 306, preferably of the chain-link type, secured at each end to the carriage and trained over idler pulley 308 on frame 282. The saw units 18 and 26 traverse across their respective Y and X axes underneath the gauge tables to cut the stack from below. With motor 300 running, actuator 294 is extended so that the blade tip clears the top of stack 160. With holddown 19 pressing the stack against the table, traversing motor 304 is then actuated to draw the saw through the material. When the saw completes a cut as indicated at 296', the control system retracts actuator 294 to pivot the saw to the position indicated at 296", and motor 304 is reversed to immediately return the saw to its start position, no matter at what location the cut is completed. As the saw returns in its lower position the blade top clears the lower surface of the stack so that stack gauging for the next out can be made without interference from the saw.

The saw control system automatically returns the saw immediately after the stack is cut through so that time is not wasted in running the saw to its furthest position without cutting. This would occur where stack width is less than maximum for the machine. 

1. In a panel cutting machine, apparatus for securely holding a stack of sheet material with respect to a cutting station while a cutter traverses along its cutting path through the material, the material being indexed for gauging along an axis, including the combination of: a pair of hold-downs, each being mounted at the cutting station traversely of the axis on either side of the cutting path for movement to and from the stack on the stack side opposite from the cutter; actuator means on either end of each hold-down to extend respective hold-downs to the stack during cutting and retract the hold down from the stack for subsequent stack indexing; support means on either end of the cutting path on the stack side opposite from the hold-downs to support the stack as the hold-downs are operated; and means for simultaneously and uniformly operating the actuator means to bring the hold-down toward the support means with its leading edge parallel thereto during such movement.
 2. The invention of claim 1 and further characterized in that the actuators comprise at least two double-acting extensible cylinders for each hold-down, each cylinder having a double-ended piston rod with volume discharge from either end being equal upon extension or retraction, the cylinder and rod being connected between respective hold-down ends and the cutting station; and, control means operable to actuate respective pairs of actuators for each hold-down independently of the other hold-down actuators, one actuator of each pair being connected as a master cylinder and the other as a slave cylinder, said control means connecting respective master and slave cylinders in series for extending the hold-downs to the stack and in parallel for retracting the hold-downs from the stack.
 3. The invention of claim 1 wherein a filler of relatively soft material which is readily cut by the cutter is mounted along the edge of each hold-down in abutting relationship with the stack surface, the fillers of respective hold-downs being mounted with their interface aligned along the cutting path whereby the initial cut of the cutter makes a kerf through either filler to accomodate saw vibration and operating variations, and at the same time the fillers provide close support against the stack on either side of the cutting path.
 4. The invention of claim 3 and further including cushion means mounted on either filler edge facing the stack for contact therewith during hold-down operation to prevent marring of the stack surface.
 5. The invention of claim 1 wherein the support means comprises at least one strip of material mounted along the cutting path in facing relationship with the surface of the stack, said material being selected to provide rigid support against pressure from the stack and being adapted to be cut by the cutter during an initial traverse of the path without injuring the cutter to automatically accomodate cutter vibration and operating variations.
 6. The invention of claim 5 wherein the support material is laminated hardwood. 